Newsletter module mailing list problems

I am having a hard time trying to set up the newsletter module (with ss 2.3.1). Whilst its working up to having a subscribe form that successfully takes details, when I look in the CMS under the Newsletter tab at the mailing list, there is only ever the last entry logged.

Also (probably being a bit thick here) but I'm lost as to what mailing list group should be selected (this necessity seems to be new to 2.3) I just want anyone to be able to sign up to the newsletter, not certain groups with certain privileges, however if an option is not selected then I just get the following error when I click on mailing list;

Fatal error: Call to a member function Members() on a non-object in /home/orangebo/public_html/pages/cms/code/MemberTableField.php on line 334

Any help here would be really greatly appreciated as Im up against time with the client!